Using the SerialPort class with USB serial devices causes application to crash when the device is surprise removed.

Using the SerialPort class with USB serial devices causes application to crash when the device is surprise removed.

Article ID : 952897
Last Review : May 9, 2008
Revision : 1.0
Source: Microsoft Support

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RAPID PUBLISHING

RAPID PUBLISHING ARTICLES PROVIDE INFORMATION DIRECTLY FROM WITHIN THE MICROSOFT SUPPORT ORGANIZATION. THE INFORMATION CONTAINED HEREIN IS CREATED IN RESPONSE TO EMERGING OR UNIQUE TOPICS, OR IS INTENDED SUPPLEMENT OTHER KNOWLEDGE BASE INFORMATION.

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Action

Write a .Net application that uses the SerialPort object to communicate with USB serial devices.  While the application is running, remove the USB device.

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Result

The application will crash due to an unhandled UnauthorizedAccessException.

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Cause

This is a known issue in the products listed below.

The reason the application is having an unhandled exception is because the .Net garbage collector is cleaning up the SerialPort object on the finalizer thread – this is where all unreferenced .Net objects have their Finalize/Dispose methods called. Part of the SerialPort.Finalize method involves using its internal Win32 handle for the COM port in a Win32 API for unmanaged cleanup. Since the Win32 handle is no longer valid (the device has been removed) this call is failing, which in turn throws the UnauthorizedAccessException.  Because this happens on the finalizer thread of the GC, it is not possible for the application to catch the exception and continue executing.

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APPLIES TO
• Microsoft .NET Framework 2.0
• Microsoft .NET Framework 3.0
• Microsoft .NET Framework 3.5

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Keywords: 
kbnomt kbrapidpub KB952897

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Microsoft Knowledge Base Article

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